RF electrode array for low-rate collagen shrinkage in capsular shift procedures and methods of use

ABSTRACT

Methods and apparatus are provided for an achieving low-rate collagen shrinkage using an electrode array comprising an elongated insulator strip having at least one pair of spaced-apart bi-polar RF electrodes, and a “channeling” disposed on the strip between the bi-polar electrodes to direct the flow of RF current therebetween. The channeling electrode is not directly coupled to the RF power source, but only indirectly through the tissue in contact with the channeling electrode. The apparatus enables low RF power levels (e.g., 0.5 watts to 25 watts) to be applied over time intervals of 5 seconds to 180 seconds to attain low-rate collagen shrinkage by directing or focusing the path of the RF current.

REFERENCE TO RELATED APPLICATIONS

[0001] This application is a divisional of co-pending U.S. applicationSer. No. 10/141,273, filed May 8, 2002, which is a continuation ofapplication Ser. No. 09/750,548 filed Dec. 28, 2000 (now abandoned),which is a continuation of application Ser. No. 09/257,359 filed Feb.25, 1999 (now U.S. Pat. No. 6,169,926), which claims the benefit of U.S.provisional Application Serial No. 60/076,199, filed Feb. 27, 1998.

FIELD OF THE INVENTION

[0002] This invention relates to RF (radiofrequency) devices and methodsfor delivering RF energy to tissue in a patient's body, and moreparticularly to an electrode array that allows for controlled low-powerRF energy delivery in orthopedic applications, for example in capsularshift procedures.

BACKGROUND OF THE INVENTION

[0003] Joint instability in adults is caused by ligaments and cartridgein a joint becoming lax or stretched, due either to the aging process orto acute trauma. Joint instability is a widespread disease and isestimated to affect up to 10 percent of the male population in the U.S.A patient's shoulder joints, knees, ankles and elbows all may becomeunstable due to lax ligaments. As a specific example, a patient'sshoulder joint (or glenohumeral joint capsule) is maintained in a stablecondition by a capsular ligament complex, subscapular tendons, rotatorcuff and teres minor muscles, among others.

[0004] Joint instability is caused by laxity in the fibrous ligamentcomplex within the joint capsule. An increase in ligament laxity may bedue to an acute-event type of trauma or recurrent minor trauma (i.e.,wear-and-tear). Often, acute-event trauma results in a unidirectionaltype of instability, whereas normal wear-and-tear results inmultidirectional joint instability. In terms of pathology,unidirectional joint instability may be defined as an excess capsularvolume (space between the humeral head and synovial surface of thecapsule) in a particular location, region or path across the capsule.Multi-directional joint instability generally may be considered to beexcessive volume within the entire joint capsule around the humeralhead.

[0005] Surgeons have developed open surgical treatments for reducing thevolume of unstable joint capsules, generally termed “capsular shiftprocedures”. In such surgery, over-stretched or lax capsular ligamentsare tightened and secured around the perimeter of the joint capsule.Such procedures frequently result in post-operative pain, loss ofmotion, nerve injury and even osteoarthritis. Further, capsular shiftpatients require lengthy post-operative rehabilitation and often do notachieve pre-injury levels of joint stability.

[0006] Surgeons also have developed minimally invasive arthroscopictechniques for performing capsular shift procedures which, for the mostpart, replicate the open procedures. An arthroscopic approach typicallyresults in less post-operative pain and reduced rehabilitation time.However, arthroscopic capsular shift techniques require high levels oftechnical expertise. Also, it is not clear whether arthroscopic ligamentfixation devices and methods are equal to those available in an opensurgical approach.

[0007] More recently, to avoid surgical reconstruction of a jointcapsule, arthroscopic surgeons have investigated the use of thermalenergy to tighten or shrink the ligaments within a joint capsule. Acapsular ligament complex includes various types of collagen, which isone of the most abundant proteins in the human body. It is well-knownthat collagen fibrils will shrink in length when subjected totemperatures ranging above about 60° C. Interstitial collagen consistsof a continuous helical molecule made up of three polypeptide coilchains. Each of the three chains is approximately equal in longitudinaldimension with the molecule, being about 1.4 nm in diameter and 300 nmin length along its longitudinal axis in the helical domain portion.

[0008] Collagen molecules polymerize into chains in a head-to-tailarrangement generally with each adjacent chain overlapping another byabout one-fourth the length of the helical domain. The spatialarrangement of the three peptide chains is unique to collagen, with eachchain existing as a right-handed helical coil. The superstructure of themolecule is represented by the three chains that are twisted into aleft-handed superhelix. The helical structure of each collagen moleculeis bonded together by heat labile cross-links between the three peptidechains providing the molecule with unique physical properties, includinghigh tensile strength and limited longitudinal elasticity.

[0009] The heat labile cross-links may be broken by thermal effects,thus causing the helical structure of the molecule to be destroyed (ordenatured) with the peptide chains separating into individually randomlycoiled structures of significantly lesser length. The thermal cleavingof such cross-links may result in contraction or shrinkage of thecollagen molecule along its longitudinal axis by as much as one-third ofits original dimension. It is such thermal shrinkage of collagenousligament tissue that can stabilize a joint capsule.

[0010] Collagen shrinks within a specific temperature range, (e.g., 60°C. to 70° C. depending on its type), which range has been variouslydefined as: the temperature at which a helical structure collagenmolecule is denatured; the temperature at which ½ of the helicalsuperstructure is lost; or the temperature at which the collagenshrinkage is greatest. In fact, the concept of a single collagenshrinkage temperature is less than meaningful, because shrinkage ordenaturation of collagen depends not only on an actual peak temperaturebut on a temperature increase profile (increase in temperature at aparticular rate and maintenance at a particular temperature over aperiod of time).

[0011] Thus, collagen shrinkage can be attained through high-energyexposure (energy density) for a very short period of time to attain“instantaneous” collagen shrinkage—the method used by all previouslyknown devices (both laser and high-energy RF waves) for joint capsuleshrinkage. These previously known treatments shrink collagenous tissuein a matter of seconds (e.g., 1-2 seconds).

[0012] Previously known methods of “instantaneous” capsular collagenshrinkage with a high energy (40 to 60 watts) mono-polar RF probe (orsimilar high-energy laser) suffer from several significant drawbacks. Insuch an RF treatment (or laser treatment), the surgeon “paints” the tipof the RF probe across a section of a joint capsule targeted forcollagen shrinkage. Because the collagen targeted for shrinkagegenerally lies well under the capsular surface, high RF energy levelsare needed-to cause shrinkage, typically 40 to 60 watts. These powerlevels, however, pose a substantial risk of ablating or perforating thesynovial surface, which is highly undesirable.

[0013] Also, as depicted in FIG. 1A, it is difficult to “paint” the RFprobe tip (even though only 3-5 mm in diameter) across the targetedportion of the joint capsule due to the limited working space betweenhumeral head H and capsule C, while still maintaining an adequateendoscopic view of the damaged or lax tissue indicated at D in FIG. 1A.At times, it may be necessary to use an lever-type instrument to pry (orretract) the humeral head away from the joint capsule to provide alarger working space, thus posing a risk of damaging the labrum (thefibrous cartilage surrounding glenoid capsule G).

[0014] Further, the previously known methods of creating “instantaneous”collagen shrinkage cause the working space between the humeral head andcapsular surface to shrink and disappear practically instantaneously,thus making it necessary to work from a first position treatmentlocation L1 toward a second location L2. Thus, it is generally notpossible to return toward the first location L1 for additional treatmentor diagnosis (see FIG. 1A).

[0015] Previously known methods of “painting” tissue with high-energy RFwaves with a hand-held probe to achieve rapid collagen shrinkage are notwell suited for collagenous tissues of different thicknesses and/or fortissue in which collagen content varies. For example, the capsularregions carrying the medial and inferior glenohumeral ligaments havesignificant collagen content (e.g., >85%) and are quite thick. Areasbetween the ligaments and around the axillary recess are quite thin.Other areas of the joint capsule contain much less collagen (e.g.,<40%).

[0016] Thus, “painting” the synovial surface with RF waves—even if theprobe is moved at a steady rate—will not cause uniform capsularshrinkage. Such free-hand techniques are technically demanding with asteep learning curve. In practice, an experienced surgeon will “paint”the RF probe tip across the capsular surface in high collagen areas, butwill stop and hold the probe tip in firm contact with thicker ligamentareas (or areas with lesser collagen), in order to apply sufficient heatto the tissue. Such start-and-stop motions, however, tend to pose a riskof ablating and perforating the synovial lining.

[0017] Moreover, there are disadvantages in using a hand-held mono-polarRF probe when relying on a thermal sensor in the probe tip to safeguardagainst surface tissue ablation. While thermal sensors are often toutedas having the ability to cut off RF delivery when tissue exceeds acertain temperature, this is generally the case only when a tissue massis firmly in contact with the sensor. In the above-described “painting”techniques, however, the probe tip contacts the tissue with varyingpressures, so that the “actual” tissue temperature may vary greatly fromthe temperature detected by the probe. Again, there is a substantialrisk that the synovial surface may be ablated or perforated byexcessively high temperatures before RF current flow is terminated.

[0018] Still other disadvantages of the previously known apparatus andmethods are associated with high-energy mono-polar RF delivery. RFenergy causes thermal effects in a tissue mass by perturbation oragitation of ions as alternating RF energy courses through the tissue inrandom paths of least resistance between the active mono-polar IFelectrode and a ground plate. As depicted in FIG. 1B, “painting” amono-polar RF probe tip across a synovial surface causes the RF pathsthrough tissue (to the ground plate) to change constantly, preventingthe perturbation of ions in any particular path or location and thuspreventing effective energy densities from being attained in anyparticular location.

[0019] Previously known methods thus achieve “instantaneous” collagenshrinkage only by using a very high current intensity (for high energydensities) that are compatible with the moving electrode (“painting”)technique. As shown in FIG. 1B, the RF current paths are onlymomentarily in a given position and not focused on the tissue that istargeted for ionic agitation. Ideally, as shown in FIG. 1C, the portionof capsular ligaments (depthwise) that need to be heated is indicated bythe shaded area.

[0020] Yet another disadvantage of previously known mono-polar IF probesrelates to the focus of RF energy created around the probe tip. Thesmall diameter of the probe tip (e.g., from 2 mm to 5 mm for reachinginto the joint capsule) when energized at high power levels causes the afocus of RF energy at the probe tip. Again, such small diametermono-polar RF electrodes require much higher energy levels than would berequired of a larger electrode to achieve a given level of thermaleffects in the joint capsule.

[0021] In view of the foregoing, it would be desirable to provideapparatus and methods for elevating the temperature of collagen tissuein a joint capsule that preferably (i) utilize relatively low RF powerlevels to prevent surface ablation, (ii) are adaptable for treatingtissues having high and low collagen content, and (iii) allow forobservation of the shrinkage at less than an instantaneous rate.

[0022] It also would be desirable to provide apparatus and methods thatshrink collagen at lower rates and at lower temperatures than obtainedwith previously known RF apparatus and methods.

[0023] It further would be desirable to provide apparatus and methodsthat create a uniform or predictable path for RF current flow throughtargeted tissue, thereby causing more uniform heating of tissue to alow-rate collagen shrinkage temperature.

SUMMARY OF THE INVENTION

[0024] In view of the foregoing, it is an object of this invention toprovide apparatus and methods for elevating the temperature of collagentissue in a joint capsule that preferably (i) utilize relatively low RFpower levels to prevent surface ablation, (ii) are adaptable fortreating tissues having high and low collagen content, and (iii) allowfor observation of the shrinkage at less than an instantaneous rate.

[0025] It also an object of the present invention to provide apparatusand methods that shrink collagen at lower rates and at a lowertemperatures than obtained with previously known RF apparatus andmethods.

[0026] It is a further object of this invention to provide apparatus andmethods that create a uniform or predictable path for RF current flowthrough targeted tissue, thereby causing more uniform heating of tissueto a low-rate collagen shrinkage temperature.

[0027] These and other objects of the present invention are accomplishedby providing an electrode array comprising an elongated insulator striphaving at least one pair of spaced-apart bi-polar RF electrodes, and a“channeling” electrode disposed on the strip between the bi-polarelectrodes to direct the flow of RF current therebetween. The channelingelectrode is not directly coupled to the IF power source, but coupledonly indirectly through the tissue in contact with the channelingelectrode. The apparatus enables low RF power levels (e.g., 0.5 watts to25 watts) to be used to attain low-rate collagen shrinkage by directingor focusing the path of the RF current.

[0028] In a preferred embodiment, bi-polar electrodes are provided infirst and second groups at each end of an elongated insulator stripadapted to be inserted into a joint capsule through a cannula. Thebi-polar electrodes are exposed on one surface of the strip, and areconnected to a suitable RF source by individual current-carrying wires.Any pair of bi-polar electrodes of the first and second groups may beselected to deliver RF energy. A channeling electrode is disposed on acentral portion of the insulator strip, spaced apart from the bi-polarelectrodes, with one surface exposed in the same direction as the activeelectrodes. The channeling electrode has no direct electrical connectionto the RF source or any of the active electrodes.

[0029] Methods of using the apparatus of the present invention toperform capsular shift procedures are also provided.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Additional objects and advantages of the invention will beapparent from the following description, the accompanying drawings andthe appended claims, in which:

[0031] FIGS. 1A-1C are schematic views showing use of a previously knownprobe to deliver RF energy to a glenohumeral joint to provide rapidcollagen shrinkage;

[0032]FIGS. 2 and 3 are perspective views of an illustrative embodimentof apparatus of the present invention;

[0033]FIG. 4 is an enlarged perspective view one end of the apparatus ofFIGS. 2 and 3;

[0034]FIG. 5 is a schematic block diagram of a controller suitable foruse with the present invention;

[0035] FIGS. 6A-6E depict a sequence of using the electrode array ofFIG. 2 to perform “low rate” shrinkage of collagenous tissue of aglenohumeral joint to treat unidirectional joint instability.

DETAILED DESCRIPTION OF THE INVENTION

[0036] The present invention provides apparatus and methods forperforming capsular shift procedures, and other similar procedures,using low levels of directed RF power (e.g., between about 0.5 watts to25.0 watts) to remodel collagen at low shrinkage rates, i.e., wherecollagenous ligament tissue is elevated to shrinkage temperatures slowlyto achieve uniform shrinkage over a large tissue mass. In the preferredembodiment, high frequency alternating RF current (e.g., from 55,000 Hzto 540,000 Hz) is directed between paired bi-polar electrodes, andthrough a targeted collagenous tissue volume, by a non-energized“channeling electrode” interposed between the bi-polar electrodes.

[0037] Alternating RF current causes ionic perturbation and frictionwithin the targeted tissue volume, elevating the tissue temperature asions follow the changes in direction of the alternating current. Suchionic perturbation thus does not result from direct tissue contact witha resistive electrode that conducts heat into tissue. In the delivery ofsuch RF energy to a soft tissue mass, I=E/R, where I is the intensity ofthe current in amperes, E is the energy potential measured in volts andR is the tissue resistance measured in ohms. In a soft tissue target,current density (or level of current intensity) is an important gauge ofenergy delivery, which further relates to the impedance of the targettissue mass.

[0038] The level of thermal effects generated within a target tissuevolume is influenced by several factors, such as (i) RF currentintensity, (ii) RF current frequency, (iii) impedance levels of tissuebetween paired electrodes, (iv) heat dissipation from the target tissuevolume; (v) duration of RF delivery, and (vi) distance through thetargeted tissue volume between the paired bi-polar electrodes.

[0039] In a preferred embodiment, the apparatus of the present inventioncomprises an elongate flexible insulator strip having dimensionssuitable for introducing the strip into a joint capsule through acannula. The insulator strip has first and second groups of bi-polarelectrodes at each end disposed facing one surface of the strip, eachbi-polar electrode facing being coupled to an RF source. A (non-active)channeling electrode is disposed in a central portion of the insulatorstrip, spaced apart from the bi-polar electrodes, and facing the samesurface of the strip as the bi-polar electrodes. The electrode arraypermits delivery of sufficient RF energy to subsurface tissue to shrinkcollagen at a low rate, while reducing the risk of desiccating orablating surface tissues.

[0040] Referring now to FIGS. 2-3, apparatus constructed in accordancewith the principles of the present invention is described. Electrodearray 5 illustratively is adapted for thermal treatment of a patient'sjoint capsule, for example a glenohumeral capsule. Electrode array 5comprises elongated member 10 carrying bipolar electrode groups 20 and22 and channeling electrode 25. Electrodes groups 20 and 22 andchanneling electrode 25 have a lower surface exposed on surface 12 ofelongated member 10.

[0041] Elongated member 10 preferably is formed from a flexiblenon-conductive material, such as any suitable medical grade plastic(e.g., vinyl), and includes insulating surface 14 that covers the uppersurfaces of all of the electrodes. More preferably, the elongated member10 comprises a transparent, or substantially transparent, material asshown in FIG. 2. Elongated member 10 preferably has dimensions thatallow it to be introduced into a joint capsule through a trocar sleeveor any minimally invasive incision.

[0042] In a preferred embodiment, elongated member 10 has a generallyrectangular cross-section having and has a thickness as thin aspracticable for an intended application. For example; for performing acapsular shift procedure in a glenohumeral joint capsule, elongatedmember 10 preferably has thickness in a range from 0.5 mm to 3 mm, awidth ranging from about 2 mm to 8 mm, and a length in a range fromabout 30 mm to 80 mm. As shown in FIG. 3, elongated member 10 preferablyis sufficiently flexible to twist about its longitudinal axis. Inaddition, elongated member 10 may comprise a resilient material capableof being springably formed to either a repose curved or linearconfiguration.

[0043] Bi-polar electrode groups 20 and 22 are provided in pairedbi-polar groups at left end 18A and right end 18B of elongated member10. Left-end bi-polar electrode group 20 comprises individual electrodes20A, 20B and 20C; right-end bi-polar electrode group 22 comprisesindividual electrodes 22A, 22B and 22C. Electrodes 20A-20C and 22A-22Cmay be fabricated from a suitable electrically conductive material, forexample, gold, nickel titanium, platinum, aluminum or copper, and areembedded in first surface 12 of elongated member 10, for example, duringa molding process.

[0044] Each bi-polar electrode (20A-20C, and 22A-22C) is connected to RFsource 40 by individual current-carrying wires 30A-30C and 32A-32C,respectively (see also FIG. 4). Accordingly, a pair of bi-polarelectrodes consisting of any of electrodes 20A-20C paired with any ofelectrodes 22 a-22C may be energized, as described in greater detailbelow. Current carrying wires 30A-30C and 32A-32C preferably are encasedin an insulated cord 42 to permit coupling of the bi-polar electrodes toPS source 40.

[0045] In accordance with the principles of the present invention,channeling electrode 25 is disposed with its lower surface exposed onsurface 12 of elongated member 10 at a position intermediate left-endgroup of electrodes 20 and right-end group of electrodes 22. Channelingelectrode 25 is not coupled to RF source 40, and is insulated and spacedapart from the “active” bi-polar electrodes. In accordance with thepresent invention, channeling electrode 25 directs the flow of RFcurrent through the tissue in contact therewith and between the selectedpair of bi-polar electrodes 20 and 22.

[0046] Channeling electrode 25 may comprise any suitable electricallyconductive material, as described above for electrode groups 20 and 22.As will of course be understood, channeling electrode may comprisemultiple discrete elements. Alternatively, channeling electrode mayextend into and overlap the region carrying bi-polar electrode groups 20and 22 (e.g., channeling electrode may take the form of rails disposedoutwardly of electrode groups 20 and 22 along the width of elongatedmember 10, and may extend for the length of the elongated member).

[0047] Still referring to FIGS. 2 and 3, elongated member 10 hasimpressed in upper surface 12 a series visual indicator marks A, B, C,and 1, 2, 3, one mark corresponding to each of bi-polar electrodes20A-20C and 22A-22C, respectively. The visual indicator marks may be anysuitable figures or symbols and provide cues that the surgeon can viewintraoperatively to determine which two bi-polar electrodes to energizefor a given procedure. Indicator marks A-C and 1-3 preferably are aslarge as possible for easy identification during an arthroscopicprocedure. The surgeon may therefore select a particular pair ofbi-polar electrodes for activation depending on which electrodes bestspan an area targeted for treatment. For example, RF current may flowfrom electrode 20A to 22A, from 20A to 22C, from 20C to 22C, etc.

[0048] With respect to FIG. 5, RF source 40, adapted to deliver bi-polarRF current between selected paired bi-polar electrodes from groups 20and 22, is described. Control panel 45 includes selectors A-C and 1-3,or alternatively, selector combinations A1, A2, A3, B1, B2, etc. (notshown) corresponding to the active electrodes or possible electrodepairings. The surgeon may, for example, press buttons on control panel45 to direct bi-polar IF current flow to and between the selectedbi-polar electrode pairing. The RF source 40, for example, may be anysuitable electrosurgical RF-generator capable of controlling energydelivery to the electrode array at low-power levels, for example, fromabout 0.5 to 25 watts.

[0049] Referring now to FIG. 6A, a schematic view of glenohumeral jointcapsule 50 is shown with synovial surface 52 overlyingcollagen-containing ligament layer 55. The end of the scapula is calledthe glenoid, and is indicated at 56 having a periosteum 58, The joint ispartly stabilized by a ring of fibrous cartilage surrounding the glenoidcalled the labrum (indicated in phantom view at 59).

[0050] To access the capsule, the surgeon makes a standard posterioraccess portal for an endoscope. A standard anterior portal then iscreated at the upper border of the subscapularis tendon and through therotator interval. A sleeve or cannula disposed through the anteriorportal allows for introduction of electrode array 5 of the presentinvention. Generally, the joint capsule is prepared for standardarthroscopic fluid inflows and outflows, although such fluids are anoptional aspect of the procedure described herein.

[0051] In FIG. 6A, the joint capsule (humeral head not shown) has laxligament portions indicated at band 60, such as may be caused by anacute-event injury and result in a unidirectional instability. As shownin FIGS. 6A-6B, the collagen ligament complex varies in thickness withinthe joint capsule, e.g., with thick area 62A and thin area 62B (ligamentthickness exaggerated for clarity). FIG. 6B shows in sectional view thedepth of capsular ligaments targeted for collagen shrinkage, the areatargeted for treatment extending from the synovial surface to theperiosteum across the lax portion.

[0052] Now referring to FIG. 6C, the surgeon introduces electrode array5 through a suitable portal or incision into joint capsule 50, so thatpower cord 42 extends out of the patient's body and may be connected toIF source 40. Electrode-array 5 may be introduced into the working spacewith a suitable instrument, e.g., a grasper, and its position isadjusted until surface 12 is positioned in contact with the capsularsurface overlying the collagenous ligament tissue targeted fortreatment, i.e., underlying band 60. When electrode array 5 is disposedin a suitable position, the surgeon may use sponges 70 (shown in phantomview) or other formable material to retain electrode array 5 in positionrelative to the humeral head (not shown) and the capsular surface.

[0053] The surgeon then identifies which pair of electrodes 20A-20C and22A-22C best span band 60 of tissue targeted for treatment. For example,in FIG. 6C, electrode 20C (with overlying visual indicator mark “C”) andelectrode 22A (with overlying visual indicator mark “1”) are bestpositioned in the joint capsule to deliver the desired thermaltreatment. The surgeon accordingly selects the appropriate controls onthe control panel 45 of RF source 40 for RF delivery to the selectedpair of electrodes.

[0054] In FIG. 6D the joint capsule is shown with arrows 125 indicatingthe path of the RF current flowing between the selected pair of bi-polarelectrodes. Of particular interest to the invention, RF energy flowsbetween electrode 22A and electrode 20C and through the tissue incontact with intermediate channeling electrode 25. As indicated byarrows 125, the RF current generally flows through the collagenoustissue directly under channeling electrode 25 (in band 60) that istargeted for treatment along similar “directed paths” for the entiretime the electrodes are -activated. By contrast, in the previously knownmono-polar RF delivery methods depicted in FIGS. 1, the current flow isin a constant state of flux.

[0055] It has been determined that the channeling electrode of thepresent invention generally confines the IF current path to the tissueregion proximate to conductive element as indicated by arrows 125. Thisis highly desirable because stray RF current flow between the bipolarelectrodes is largely eliminated, thereby providing higher currentdensity (energy density) in the targeted tissue with lower RF powerlevels.

[0056] Moreover, the RF current travels generally parallel to channelingelectrode 25, thereby heating the entire depth of collagen tissue anddeveloping a fairly uniform thermal gradient from capsular surface 52 toperiosteum 58. This aspect of the invention is to be contrasted withpreviously known mono-polar RF delivery, wherein the capsular surfacereceives excess heat (possibly ablating surface 52) and RF current flowbetween the probe and ground plate is perpendicular to the surface, orrandom.

[0057]FIG. 6E shows the joint capsule after shrinking collagen inligament 55 with the capsular surface shifted toward the humeral head(not shown) along band 60 (electrode array 5 is shown in phantom viewand the extent of capsular shift is exaggerated for purposes ofillustration). By thus directing RF current along the desired path alongand below synovial surface 52, it been found that RF current intensitycan be reduced significantly, when compared to previously knownmono-polar devices and methods.

[0058] The method of the present invention thus utilizes a stationaryelectrode (rather than a painting technique), with the bi-polarelectrodes and channeling electrode pressed against capsular surface 52.In a preferred method of the present invention, RF current is appliedfor times ranging between 5 seconds and 180 seconds at powers in a rangeof 0.5 to 25 watts, more preferably 2 to 20 watts, and still morepreferably, 2 to 10 watts. The duration of RF current for low-ratecollagen shrinkage more preferably ranges from 10 seconds to 120seconds, and still more preferably, from 20 seconds to 60 seconds.

[0059] Compared to the rapid shrinkage of previously known systems(typically 1 to 2 seconds), the longer time intervals provided by thepresent invention allow “lowrate” collagen shrinkage, affording thesurgeon sufficient time to evaluate the extent of capsular shrinkage andto terminate RF energy delivery based on observation. Using theapparatus and methods of the present invention, the surgeon simply mayterminate the low-level RF power at any time during capsule shrinkage togauge the correct amount of shrinkage. After shrinking targeted ligamenttissue in the first location, the surgeon then may move electrode array5 to a second location.

[0060] It should be appreciated that applications of the electrode arrayof the present invention may be generalized to deliver controlled levelsof radiofrequency energy to subsurface tissues at other locations in abody for a variety of therapeutic purposes, such as for bio-stimulationor bio-excitation purposes.

[0061] Although particular embodiments of the present invention havebeen described above in detail, it will be understood that thisdescription is merely for purposes of illustration. Specific features ofthe invention are shown in some drawings and not in others, and this isfor convenience only and any feature may be combined with another inaccordance with the invention. Further variations will be apparent toone skilled in the art in light of this disclosure and are intended tofall within the scope of the appended claims.

I claim:
 1. A method of delivering RF current from a IF source to tissuein a medical procedure comprising contacting a first tissue region witha first electrode, contacting a second tissue region with a secondelectrode spaced apart from the first electrode, contacting a thirdtissue region with a third electrode spaced intermediate the first andsecond electrodes, coupling the first and second electrodes, but not thethird electrode, to a source of RF current, and applying the RF currentbetween the first and second electrodes, the third electrode serving todirect a path of RF current through the third tissue region.
 2. Themethod of claim 1, further comprising applying the RF current betweenthe first and second electrodes at a power in a range of about 0.5 to 25watts.
 3. The method of claim 1, further comprising applying the RFcurrent between the first and second electrodes at a power in a range ofabout 2 to 10 watts.
 4. The method of claim 1, further comprisingapplying the RF current between the first and second electrodes for atime period in a range from about 5 to 180 seconds.
 5. The method ofclaim 1, further comprising applying the RF current between the firstand second electrodes for a time period in a range from about 10 to 60seconds.